(1) Field of the Invention
This invention relates to hydrocarbon polymer modifiers and their use in elastomeric compositions. More particularly, this invention relates to hydrocarbon polymer modifiers having a balance of properties including molecular weight, softening point, and aromaticity.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Hydrocarbon resins are used in a variety of applications. In elastomeric compositions, for example, hydrocarbon resins are used as a processing aid and to improve the characteristics of elastomeric composition, e.g., in tire components, such as treads and sidewalls, hoses, belts, footwear components, and vibration isolation devices. The selection of ingredients for the commercial formulation of an elastomeric composition depends upon the balance of properties desired, the application, and the end use for the particular application.
Generally, the raw ingredients and materials used in tire compounding impact all tire performance variables, thus, the ingredients must be compatible with the rubbers, not interfere with cure, be easily dispersed in all tire compounds, be cost effective, and not adversely impact tire performance. Rolling resistance, dry and wet skid characteristics, heat buildup, and so on, are important performance characteristics, as well as the ability to improve the endurance of tires used in a wide variety of conditions, such as is required for agricultural tires, aircraft tires, earthmover tires, heavy-duty truck tires, mining tires, motorcycle tires, medium truck tires, and passenger car tires. On the other hand, maintaining ease of processability of the uncured elastomeric composition is also of significant importance. Additionally, the goals of improving air impermeability properties, flex fatigue properties, and the adhesion of the elastomeric composition to adjoining tire components without affecting the processability of the uncured elastomeric composition or while maintaining or improving the physical property performance of the cured elastomeric composition still remain.
Conventionally, various processing oils, such as naphthenic, paraffinic, and aromatic oils, have been added to most tire components to aid compound processing. Aromatic oil has been preferred due to its processing effectiveness and beneficial secondary properties, e.g., adhesion. However, these processing oils, particularly aromatic oils containing distilled aromatic extracts, are being replaced due to health, safety, and environmental concerns. Current industry PAH (polycyclic aromatic hydrocarbon) oil replacement options, such as treated distillate aromatic extracts (“TDAE”) and mild extract solvates (“MES”), are limited in supply and have shown deficiencies, such as reduced dynamic properties, reduced tire wet traction performance, reduced tear strength, and reduced tire durability. For example, tire component-to-component adhesion may be less with TDAE and MES than with conventional aromatic oils. Therefore, a need exists for better replacements for processing oils in tire and tire tread compounds which will maintain beneficial compounding properties without adversely impacting tire performance.
It is known to improve rubber compounding with resins which are compatible or soluble in the rubber base, and which have a high softening point and low molecular weight. With some elastomers, however, the resin requires a relatively high aromatic content for compatibility. The aromatic compounds, however, tend to reduce the softening point of the resin. The softening point can be elevated by using a higher cyclics content, but this leads to undesirably increased and/or broadened molecular weight and agglomeration of the resin pellets.
There is a need for a resin with a balance of properties including softening point, Tg, aromaticity, molecular weight, and molecular weight distribution.